The disclosure relates to a pull-out guide for furniture parts that can be moved in relation to each other, comprising at least two pull-out rails having at least one running surface. At least one first rolling element and at least one second rolling element are arranged between the pull-out rails, which rolling elements are rotatably retained in a rolling-element cage, wherein the at least one first rolling element and the at least one second rolling element have an identical nominal diameter.
Pull-out guides for furniture parts that can be moved in relation to each other such as drawers which are movably mounted in a furniture body are known from the prior art, e.g. from the publication DE 3 536 654 C2. Rotatably mounted cylindrical rollers or balls are used as rolling elements in the rolling-element cage. “Hard” steel balls or rollers are frequently used because they allow smooth guidance even under high mechanical loads by a heavy weight which is movably held by the pull-out guide. A loud rolling noise can be disadvantageous however.
For the purpose of reducing the rolling noises, it is known to use plastic rolling elements in drawers which need not carry any exceptionally high weights. There is a problem in respect of the plastic rolling elements, however, that prolonged idle times can lead to a flattening of the rolling elements. The flattening of the plastic rollers is reversible. The plastic rollers are thoroughly kneaded by a subsequent actuation of the pull-out guide and assume their original form again. Vibrations occur initially as a result of the flattened portions and consequently to an increased running noise (“rumbling”).
A pull-out guide for drawers is described in the publication EP 1 959 794 B1, in which rolling elements with different diameters are inserted. The pull-out rails of the pull-out guide are formed in such a way that in the closed state of the drawer only the first rolling element with the smaller diameter is loaded. For this purpose, one of the guide rails comprises an elevation facing the rolling elements in a front end region. After the opening of the drawers, the first rolling element leaves the region of the elevation so that subsequently the guide rails run on the second rolling elements with the greater diameter. In the closed state of the drawer, i.e. in a retracted state of the pull-out guide, only the first rolling element with the smaller diameter is loaded, as a result of which only this rolling element is subjected to a deformation. Since subsequently guidance occurs by means of the second rolling element with the greater diameter, the deformed first rolling element does not lead to an increased running noise.
It is disadvantageous in this assembly, however, that an additional rolling element is provided with the first rolling element, which is not loaded in the normal operation of the drawer. Said additional first rolling element leads to an increased input of material and thus additional costs with the consequence that it does not contribute to the running properties in normal operation. For example, it does not increase the maximum weight which can be carried by the pull-out guide.
The present disclosure illustrates and describes a pull-out guide in which an increased running noise after a prolonged idle time of the pull-out guide is suppressed, without providing additional rolling elements that are not used in normal operation.
A pull-out guide in accordance with the disclosure and of the type mentioned above is characterized in that at least one of the running surfaces has a free-running segment in which the at least one first rolling element is positioned in a retracted state of the pull-out guide, wherein the running surfaces have a greater distance from each other within the free-running segment than outside the free-running segment.
As such, the first rolling element may be engaged with both running surfaces outside the free-running segment and engaged with only one of the running surfaces within the free-running segment. Therefore, only the at least one second rolling element carries the load during the idle time. Accordingly, only the second rolling elements are potentially deformed during a prolonged idle time. If the pull-out guide is moved from the retracted state, the at least one first rolling element leaves the free-running segment, comes into engagement again with the two regular running surfaces and takes up the weight again that is carried by the pull-out rails or the load acting on the pull-out rails.
Since the first rolling elements have passed their idle time in the free-running segment, they do not contain any flattened portions, optionally in contrast to the second rolling elements. Even if the second rolling elements show flattened portions, said flattened portions do not impair the running properties because the distance of the pull-out rails from each other is determined by the first rolling elements. In the respective rotary position of the deformed second rolling elements, in which the flattened portions face the running rails, the upper carried pull-out rail does not follow the shape of the second rolling element but moves its weight entirely to the first rolling element.
In an embodiment of the pull-out guide, the free-running segment is formed as a bead, a recess, an embossed portion or as a ramp. The free-running segment thus formed is preferably integrated in one of the running surfaces. The aforementioned configurations represent embodiments of the free-running segment which are easy to realise and can be integrated in the running surfaces with ease.
In a further embodiment, the first rolling elements are not in contact with the two running surfaces in the retracted state of the pull-out guide, between which they are arranged. It is thus securely ensured that the first rolling elements are not deformed during an idle period.
In a further embodiment of the pull-out guide, the distance between the running surfaces within and outside the free-running segment differs by less than 10%, for example, by less than 5% of the diameter of the first and second rolling elements. These differences in distance may be adequately large for relieving the first rolling elements. At the same time, these differences in distance may be sufficiently small to be realised very well in the running surfaces and the guide rails without leading to influences on the dimensioning of the guide rails.
In a further embodiment of the pull-out guide, several first rolling elements and/or several second rolling elements are arranged within a rolling element cage one after the other in the longitudinal direction of the pull-out guide. The free-running segment may have a length which is at least as great as the maximum distance of two of the multiple first rolling elements. In addition, further rolling elements can be provided. As a result, the invention can be used in rolling element arrangements with several rolling elements.
In a further embodiment of the pull-out guide, the first and/or second rolling elements and/or optionally the further rolling elements consist of plastic. A reduced rolling noise of the pull-out guide can be achieved with plastic rolling elements. Since the rumbling noises which occur in the plastic rolling elements after a prolonged idle time can be prevented by the free-running segment in accordance with the invention, the plastic rolling elements are especially suitable within the scope of the invention. Since the first rolling elements which are not deformed after a prolonged idle time determine the distance of the running surfaces of interacting guide rails, a potential flattening of the second rolling elements does not lead to a rumbling noise. Plastic can therefore also be selected as the material for the second rolling elements within the scope of the invention.
In a further embodiment of the pull-out guide, the first and second rolling elements and optionally the further rolling elements differ from each other with respect to their geometry, their material, their hardness and/or their width. The further rolling elements can further differ with respect to their diameter from the first and second rolling elements. The free-running segment in accordance with the disclosure, in the case of a nominally identical diameter of the first and the second rolling elements, leads to the desired relieving effect of the first rolling elements in the retracted state of the pull-out guide.
Irrespective thereof, other material properties and/or geometries of the different rolling elements, and also different diameters for the further rolling elements, can be selected in order to achieve optimal running properties.